GB2202649A

GB2202649A - Direct drive electric motor control

Info

Publication number: GB2202649A
Application number: GB08804822A
Authority: GB
Inventors: Yutaka Ono; Yayoi Tsuchiya; Yutaka Koizumi; Hitoshi Morimoto; Hideo Banzai; Yasuhiko Muramatsu; Syotaro Shindo; Toshihiro Kanehara; Norihiko Hatano; Susumu Ohta; Mitsuhiro Nikaido
Original assignee: Yokogawa Electric Corp
Current assignee: Yokogawa Electric Corp
Priority date: 1987-03-02
Filing date: 1988-03-01
Publication date: 1988-09-28
Anticipated expiration: 2008-03-01
Also published as: US4843292A; FR2613886B1; DE3806752A1; KR880011990A; KR910000099B1; GB8804822D0; GB2202649B; FR2613886A1; DE3806752C2

Description

11 1 2202649 DIRECT DRIVE ELECTRIC MOTOR SYSTEM This invention relates to

a direct drive electric motor system for use for example in driving the joints of a robot of the multi-joint type.

A drive system having a D.C. motor and a decelerator Is the main type used f or example f or the purpose of driving the joints of a robot of the multi-joint type in which a low speed and large torque are needed.

However, an ideal system is one that employs a direct drive (abbreviated as D.D.) system utilizing a motor of the inductor type, the improvement being in relation to the life of the brush of a D.C. motor, the decelerator of the D.C. motor and the necessity for maintenance of lubrication oil.

A circuit for driving such a motor is known in which an exciting current passing through the coil of the motor is detected by means of an electric current detecting circuit. Then the difference between the thus detected current and a predetermined instructed current level is supplied to an electricity amplifying circuit, wherein an exciting current is passed through the motor coil in such a manner that the differential signal becomes zero by means of a pulse width modulation signal (PWM signal).

In the driving circuit of the type described above, a current detecting circuit preferably has a high degree of accuracy and insulating capability and a simple structure.

2 A type of means for detecting the rotation of such a motor is known in which an optical rotary encoder or a magnetic resolver is used. The means for detecting the rotation of the motor is preferably capable of detecting at a high resolution the rotational position, rotational speed and the position ofthe magnetic poles of the motor. Furthermore, the means for detecting the position of the motor is preferably capable of detecting ea sily the original point of the rotational position.

As a circuit for controlling the rotation of the motor, a device is known in which the rotational speed of the motor and the rotated position are controlled in a feedback manner in response to a detection signal from the rotation detecting means. A control circuit of the type described above is preferably capable of adjusting the servo systems in accordance with the conditions for use of the motor, for example, the characteristic frequency of the motor or load inertia.

As a device for stopping the motor, one type is known in which the coil of the motor is separated from the driving circuit when the motor is stopped so as to generate a short circuit, whereby the motor is stopped by way of consuming the kinetic energy due to Joule's effect by way of the resistance of the coil.

In a stopper device of the type described above, when the motor rotates at a high rotational speed, the phase difference (abbreviated as 11phaseY'I hereinafter) 1 3 between the exciting current and the exciting voltage becomes large due to the inductance of the coil. Therefore, the kinetic energy cannot be consumed efficiently. The motor which is used for driving joints of a robot is stopped at a variety of rotational speed ranges. Therefore, a stopper device of the type described above is not suitable for such use.

It is known to use rectangular slits in the optical encoder as the rotation detecting means.

However, since such a rectangular slit creates a spatial distribution of the passing light in the form of a rectangular shape, means for detecting the passing light receives the rectangularly distributed light. Therefore, the detectJon signal includes in principal higher harmonics. If the detection signal of the type described above is used for controlling the motor, ripples are included in the position and speed signals. As a result of this, a problem arises in that the motor cannot rotate smoothly.

As described above, the direct drive motor (abbreviated as "D.D. motor" hereinafter) system needs to satisfy many factors. However, a system which can simultaneously satisfy all the above requirements has not - yet been realized.

An object of the present invention is to realise a D.D. motor system which can simultaneously satisfy the above described requirements.

4 According to the present inention, a direct drive motor system comprises a motor portion of an Inductor type; a rotation detecting portion for detecting the rotation of a rotor of said motor portion; a position control portion for obtaining the difference between an instruction signal on the rotational position and a detection signal from said rotation detecting portion, and outputting a control signal depending upon the thusobtained difference by making use of a tertiary servo system with a software; a speed control portion for obtaining the difference between an output signal from said position control portion and said detection signal from said rotation detecting portion, and for outputting a control signal depending upon thus-obtained difference; a driving circuit for detecting an exciting current passing through a coil of said motor portion, obtaining the difference between a detection signal of said exciting current and an output signal from said speed control portion, and controling said exciting current depending upon thus- obtained difference; and a tuning portion for adjusting servo systems of said speed control portion and said position control portion. 25 Thanks to the above characteristics, the system according to the present invention is able to simultaneously satisfy the various conditions which need to be provided for with respect to the direct drive motor. In order that the invention may be clearly understood and readily carried into effect direct drive motor systems in accordance therewith will now be described, by way of example, with reference to the accompanying drawings, in which:

Fig. 1 is a block diagram illustrating the structure of a D.D. motor system embodying the present invention; Fig. 2 is a circuit diagram of an example of the D.D. motor system shown in Fig.1; Figs. 3(a) and 3(b) are respectively a sectional front elevation and sectional side elevation of a portion of a motor; Fig. 4 is a circuit diagram of an example of a current detecting circuit of a driving circuit; Fig. 5 is a graph; Fig. 6 is a circuit diagram; and Figs. 7(a), 7(b), 7(c) are graphs Illustrating an operation of the circuit shown in Fig. 4; Figs. 8, 9, 10 are circuit diagrams of an example of a rotation detecting portion; Fig. 11 is an example of a gain table stored in a position control portion; Fig. 12 is a circuit diagram of a portion of another system embodying the present invention; Figs. 13 and 14 are equivalent circuit diagrams of a control portion shown in Fig. 12; 6 Figs. 15(a) and 15(b) are graphs showing characteristics of a stopper portion; Fig. 16 is a diagram of an example of a slit arrangement used in a rotation detecting portion shown in 5 Figs. 8 to 10; Figs. 17 and 18 are diagrams showing the structure of slits shown in Fig. 16; Fig. 19 is a circuit diagram of another example of a rotation detecting portion used in an embodiment of the present invention; Figs. 20(a), 20(b) are graphs showing an operation of the circuit shown in Fig. 19; Fig. 21 shows a waveform of an output signal from an encoder having sine- wave formed slits; Figs. 22(a), 22(b) are respectively a front elevation and a cross-section on line Z-Z of Fig. 22(a) of a rotation detecting portion used in an embodiment of the present invention; Fig. 23 is a circuit diagram of the detcting portion shown in Figs.22(a), 22(b); Fig. 24 is a block diagram of a counter circuit which uses the device shown in Figs. 22(a), 22(b); Figs. 25(a), 25(b) are respectively a front elevation and a cross-section of another example on line Z1-z, of Fig. 25(a) of a rotation detecting portion used in an embodiment of the present invention; and Figs. 26, 27, 28 are circuit diagrams relating to 7 the rotation detecting portion shown in Figs.25(a), 25(b). Referring to Fig. 1, reference numeral 100 represents a motor portion, reference numeral 200 represents a driving circuit for rotating the motor portion 100. Reference numeral 300 represents a rotation detecting portion for detecting the rotation of the motor portion 100. The rotation detecting portion 300 comprises, for example, an encoder 3001 and an encoder interface (abbreviated as "encoder I/W' hereinafter) 3002. Reference numeral 400 represents a speed control portion for feedback-controlling the rotational speed of the motor portion 100. Reference numeral 500 represents a position control portion for feedback-controlling the rotational position of the motor portion 100. Reference numeral 600 represents 15 a tuning portion for adjusting the servo systems of the speed control portion 400 and the position control portion 500.

Referring to Fig. 2, the motor portion 100 comprises a motor of a threephase inductor type in which a rotor is disposed on the outside thereof, while a stator is disposed on the inside thereof. The specific structure of the motor portion 100 is shown in Fig. 3.

Fig. 3 (A) is a front elevational view of the motor portion 100. Fig. 3 (B) is a cross-sectional view of the motor portion 100.

In order to make the radius of the rotor of the motor large, the rotor is disposed on the outside, while 8 the stator is disposed on the inside. Furthermore, a static magnet is disposed on the stator side.

Reference numeral 101 represents an inside stator comprising two magnetic materials 101a and 101b, a static magnet (permanent magnet or electromagnet) 102, and an exciting coil to be described hereinafter.

Each magnetic material 101a and 101b has six salient poles 103a, to 105al, 103a2 to 105a2 and 103b, -to 105b, and 103b2 to 105b2. At each front end of the salient poles is provided with teeth with pitch P. The teeth on the neighbouring salient poles, for example, the teeth on 103a, and 104a2, are shifted by 1/3 pitch (P/3) wi-th respect to each other. On the other hand, the salient poles opposing each other of the two magnetic materials 101a and 101b are, for example, the salient pole 103a, and the salient pole 103b, are, arranged to be in the same phase. Reference numerals 106a to 106c and reference numerals 107a to 107c represent exciting coils, two of them, that is, the exciting coils 106a and 107a, 106b and 107b and 106c and 107c being connected in a series manner. Reference numeral 108 represents a rotor made of a magnetic material having teeth of pitch P on the inside thereof. The rotor 108 comprises the members 108a and 108b and the teeth thereof are shifted by 1/2 pitch.

The motor constituted as described above rotates when the currents (sine wave, pulse wave or the like) the phases of which are shifted by 1200 are passed through the 9 exciting coils 106a and 107a, 106b and 107b, 106c and 107c. The direction of rotation of this motor can be switched by changing the advance or delay of the phases of the currents. The flux generated by the static magnet 102 and the flux generated by the exciting coil 106a are added or subtracted each other at gaps 109a and 109b. As a result of this, a pulse motor rotates at a high resolution. Since the flux generated by the static magnetic 102 satisfies half of the flux needed for rotating this pulse motor, electricity consumption can be kept low, and efficiency is thereby Improved. The permanent magnet employed as the static magnet is disposed on the stator side because the magnetic flux density at the surface of the magnet is small, that is, at most 1T (tesla), therefore a certain size is needed for the permanent magnet, but if it is disposed on the rotor side, the thickness in the radial direction becomes large. The number of the salient poles may be selected from multiples of three other than six. 20 The motor described above can generate a significantly large torque with respect to a motor of the same outer diameter and same shaft diameter. Referring back to Fig. 2, the driving circuit 200 will now be described. 25 Reference numerals 201 and 202 in the driving circuit 200 represent current detecting circuits for detecting the exciting currents which pass through coils L, and L2 of the motor portion. Reference numerals 203 and 204 represent subtractors for obtaining the difference between the current Instruction value supplied from the speed control portion 400 and detected currents from the current detecting circuits 201 and 202. Reference numeral 205 represents an electricity amplifying circuit which serves to turn on or of f a transistor of an exciting circuit 207 by supplying a PWM signal generated by a PWM circuit 206, the PWM signal being generated in response to signals from the subtractors 203 and 204. As a result of this, three phase sine-wave current Is passed through the motor in such a manner that the differential current between the subtractors 203 and 204 becomes zero.

The specific structures of the current detecting circuits 201 and 202 are shown in Fig. 4.

in Fig. 4, symbol X, represents an input circuit, symbol X2 represents an output circuit, and symbol TR represents a transformer.

The transformer TR comprises a primary coil nj to which the input circuit X, is connected, a secondary coil n2 to which the output circuit X2 is connected, and a third coil % which is disposed between the primary coil nj and the secondary coil n2.

Symbols d, and d2 in the input circuit X, represent input terminals which are connected to a line - through which the exciting current shown in Fig. 2 passes.

Symbol r represents a resistor which is connected 11 between the input terminals dl and d2. Exciting currents I from the motor coils L, and L2 pass through the resistance r. A series circuit formed by a resistor R, and a capacitor Cl is connected to the resistor r in a parallel manner. The magnitude of resistance of the resistor r is, for example, substantially 5m-Q which is sufficiently small with respect to the magnitude of the resistor R,. Furthermore, a series circuit formed by a parallel diode circuit D, and the primary coil nj is connected to the capacitor Cl in a parallel manner. The parallel diode circuit D, comprises diodes D,, and D12 which are connected in parallel in such a manner that they form a reversed polarity.

Symbols d3.and d4 in the output circuit X2 represent output terminals. A series circuit formed by a low-pass filter (abbreviated as IlLPFI1 hereinafter) F, a resistor R2, and a capacitor C2 is connected to the pl ace between the output terminals d3 and d4. A series circuit formed by a parallel diode circuit D2 and the coil n2 is connected to two ends of the capacitor C2 which forms averaging means. The parallel diode circuit D2 is constituted in a similar manner as that for the parallel diode circuit D1.

The relationship between the voltage el and the passing current il which is applied to and passes through the parallel diode circuits D, and D2, is non-linear as shown in Fig. 5.

12 Symbol OS represents a pulse generator which is connected to the coil % through a resistor R3 and a capacitor C3.

In the circuit constituted as described above, when the proportion of the number of coils of the primary coil ni and the secondary coil % Of the transformer TR is set at 1:1, and symmetrical positive and negative inpulse signals are supplied to the third coil n3, the equivalent circuit of this becomes as shown by Fig. 6.

In the equivalent circuit show in Fig.6, input voltage Ei becomes rI (resistance of the resistor r is also represented by r).

Switches S, and S2 serve to switch diodes D,,, D12, D21 and D22. When a positive inpulse from the pulse generator OS is applied to the switches S, and S2, they are connected to a contact g, side (diodes D,, and D21 are conductive). On the other hand, when a negative inpulse is applied to the switches S, and S2, they are connected to a contact g3 side (diodes D12 and D22 are conductive).

Furthermore, in a case where any inpulse is not applied, the switches S, and S2 are connected to the contact 92 side (both of the diodes are not conductive). Each of the diodes D11 to D22 is expressed by series connection by a forward voltage A and a kinetic resistance (forward resistance) r.

In a state where a positive inpulse io is being applied from the pulse generator OS, the switches S, and 13 S2 become the equivalent (diodes D,, and D21 are conductive) state to the state where they are connected to the contact g,, therefore the inpulse io passes to the diode D,, side and the diode D21 in such a manner that the 5 equal magnitude of the io/2 passes to the above two sides. In this state, an output voltage E 01 between the output terminals d3 and d4 can be expressed by Equation 1.

E Ei + An + -jQ (rj, - r21) - A21 no# 01 2: 2 Furthermore, in a state where the negative inpulse io (tha m plitude is assumed to be the same as the case of positive) is applied, an output voltage E02 between the output terminals % and d4 can be expressed by Equation 2.

E Ei '0 (r12 - r22) + A22...'...2 02: _. AI 2 - 7 By applying the positive and negative inpulses from the pulse generator OS as shown in Fig. 7(a) at a repetition period of T, and making the capacities of the capacitors C, and C2 suf f iciently large so as to make the 20 change in potential due to charge or discharge of the inpulses small, the output voltage Eo becomes a mean of E01 and E02, thereby it can be expressed by Equation 3 from Equations 1 and 2.

Eo Ei ±2-(hii - A12 - A21 + A22) + i-4L (rll'- r12 - r21 + r22) 14 in Equation 3, if A12P '21 = A22 rj, r12P r21 = r22 both the second and third terms become zero, that Is, the output voltage EO and the input voltage Ei become the same. Therefore, the voltage Ei supplied to the input circuit can be obtained from the output circuit side in an electrically insulating manner.

The conditions shown in Equation 4 can be easily achieved by way of using the same standardised part for the devices D,, and D12, and for the devices D21 and D22 which form the parallel diode circuit, or maintaining a certain temperature.

Fig. 7 illustrates waveforms generated when the circuit shown in Fig. 6 is actuated, wherein Fig. 7(a) shows inpulses of positive and negative polarities, Fig.

7(b) shows the currents divided into the D, side and D2 side of the parallel diodecircuit, and Fig. 7(c) shows an output voltage in which the magnitude corresponding to the ripple of the output voltage Eo is shown exaggeratedly.

Referring back again to Fig.2, the structure of the rotation detecting portion 300 will now be described.

The structure of an encoder I/F3002 will now be described. Fig. 8 illustrates an example of the structure 1 of the encoder I/F3002.

Referring to this figure, reference numeral 301 represents an annular code-plate having light penetrating slits formed In two-stage arranged In the circumferential direction thereof, each of the slits being disposed at a predetermined pitch. The outer slit configuration comprises m, light penetrating slits 302, while the inner light penetrating slit configuration comprises m2 light penetrating slits 303. These light penetrating slit configurations 302 and 303 are provided for the purpose of detecting the shift of the teeth provided for the rotor 108 and the stator 101 of the motor. Slits S are provided for the purpose of detecting the original point at positions outside the slit configuration 302, whereby the rotational position of the code plate 1 can be detected.

This code plate 301 is arranged to rotate together with the output shaft of the motor.

Reference numerals 304 and 305 represent light sources, reference numerals 306 and 307 represent lenses for converting the light beams from the light sources 304 and 305 to parallel beams.

The light passed through the lens 306 reaches the slits 302 and the slits S, while the light passed through the lens 7 reaches the slits 303.

Reference numeral 308 represents an image sensor which receives the light (slit image) passed through the light penetrating slits 302, and which comprises, for 16 example, eight photodiodes 3081 to 3088 which are disposed in an array configuration. Symbols G, and G2 represent photodiodes for detecting the ight beams passed through the light penetrating slits S.

Reference numeral 309 represents an image sensor for receiving the light (slit image) passed through the light penetrating slits 30 3, the image sensor 309 being constituted by, for example, eight array-like arranged photodiodes 3091 to 3098.

These photodiodes are, as shown in Fig. 9, arranged within one pitch P' formed by two penetrating slits.

Reference numeral 310 represents a signal processing circuit in which the positional relationship between the rotor 108 and the stator 101 of the motor is calculated in response to the detection signals from the photodiodes 3081 to 3088 those from the photododes 3091 to 3098.

An example of the specifical structure of such a control device is shown in Fig.10.

Referring to Fig. 10, symbols SW1 to SW8 represent switches for successively obtaining signals from the corresponding photodiodes 3081 to 3088 and photodiodes 3091 to 3098 at a predetermined timing.

Reference numerals 311 and 312 represent OP amplifiers for amplifying the signals which are applied thereto through the corresponding switches SW1 to SW8. The outputs from the OP amplifiers 311 and 312 form a waveform in a step-like shape. Each height of the waves is 17 determined in accordance with the number ofthe photodiodes which have detected the light.

Then referring back to Fig. 2, the structure of the encoder I/F 3002 will now be described.

LPFs 313 and 314 of the encoder I/F3002 extract the low frequency components of the outputs from the OP amplifiers 311 and 312. Comparators 315 and 316 shape the waveforms of the outputs f rom the LPFs 313 and 314.

Period counters 317 and 318 count the period of the waveforms of the outputs from the comparators 315 and 316.

Reference numeral 319 represents a phase difference counter for counting the phase difference between the output waveforms from the comparators 315 and 316.

Then, the structure of the speed control portion 400 will now be described.

Reference numeral 401 of the speed control portion 400 represents a switch for switching the speed control mode and the position control mode. The switch 401 is turned to the contact h, when the speed control is performed, while it is turned to the contact h2 when the position control is performed. Reference numeral 402 represents an F/V converter for converting the output signal from the encoder I/F3002 to a speed signal.

Reference numeral 403 represents a subtractor for subtracting between the signal (serves as an instruction value on speed) from the switch 401 and a signal from the F/V converter 402.

18 Reference numeral 404 represents a multiplying digital-analog converter (abbreviated as 11MDA" hereinafter) In which the gain is converted In response to a digital signal whereby analog Input signals are amplified. A signal for setting the gain is supplied from the position control portion 500 or the tuning portion 600.

Reference numeral 405 represents a voltage control limiter (abbreviated as 'WCL11 hereinafter) which limits the output from the gain 404 to a predetermined upper limit or a predetermined lower limit.

Reference numerals 406 and 407 represent MDAs which receive a signal from the VCL 405, and supplies current signals I sin Oe or I sin (ge + 1200) as a current instruction value to the subtractors 203 and 204 in response to the commutation control signal from the position control portion 500 (wherein symbol I represents a current).

The structure of the position control portion 500 will now be described. In the position control portion 500, reference numeral 501, represents a counter for generating a position instruction signal in response to a position instruction pulse signal and a rotational direction signal. Reference numeral 502 represents a switch which is connected to a contact ki in a normal mode, and is connected in a test mode to a contact k2 to which a test 19 signal is supplied by a test signal generating means 5021. Reference numeral 503 represents a subtractor which obtains the difference between a signal (serves as a position instruction signal) from the switch 502 and a 5 signal from position detecting means 504.

Reference numeral 505 represents position control means for adjusting a gain of the MDA 404 basing on a parameter read from a gain table 506 in response to a signal from the turning portion 600. Position control means 505 forms a tertiary servo system for performing IPD (Integration, proportion, and differentiation) by means of a software.

The gain table 506 comprises, as shown in Fig. 11, a table in which loadinertia J of the motor, characteristic frequency fn of the position control system, and the most suitable control parameter values X11, X12, X13 corresponding to the load inertia J and the characteristic frequency fn are shown in a corresponding manner. The gain table 506 comprises a speed controlling table and a position controlling table, and each speed control table and the position control table comprises a P-operating (proportion) table and an I- operating (integration) table.

Reference numeral 507 represents commutation control means for controlling the commutation of the motor by applying signals to the multipliers 406 and 407 in response to a signal from the encoder I/F3001. Reference numeral 508 represents a D/A converter for converting in a digital and analog manner an output from the position control means 505. Reference numeral 509 represents a sample-hold circuit (abbreviated as "S/H circuit" hereinafter) for sample-holding an output from the D/A converter 508, and supplies it to the tuning portion 600.

When the speed control is performed, the switch 401 is turned to the contact h,, whereby the difference between the analog speed input as a speed instruction value and a speed signal from the F/V converter 402 is obtained by the subtractor 403. The gain of the MDA404 is set by means of a control parameter value read out from the gain table 506 by making use of switches 601 and 602 to be described hereinafter.

When the position control is performed, the switch 401 is connected to the contact h2 and the switch 502 is connected to the contact kl, The difference between the position instruction signal from the counter 501 and the output signal from the position detecting means 504 is obtained by the subtractor 503. In the position control means 505, a control parameter is read out from the gain table 506 by means of the switches 601 and 602. The control parameter thus read out is used for adjusting the gain of the MDA404 In a position control algorithmic manner.

The structure of the tuning portion 600 will now be described.

In the tuning portion 600, reference numeral 601 and 21 602 represent servo tuning switches. The servo tuning switch 601 comprises a characteristic frequency setting switch for setting characteristic frequency fn in a plurality of steps within a predetermined range. The characteristic frequency is, for example, set into 16 steps in a range of 5 to 20Hz by means of this switch 601. Reference numeral 602 represents an inertia setting switch for setting inertia J into a plurality of steps within a predetermined range.

When fn and J are set by means of these switches 601 and 602, a most suitable control parameter value which corresponds to the set values of f n and J is read out from the gain table 506.

When position control is performed by means of the switches 601 and 602, the position control means 505 adjusts the gain of the MDA404 depending upon the control parameter value read out from the position controlling table. When speed control Is performed, the gain is adjusted by way of supplying the control parameter read from the speed control table to the MDA404.

Reference numeral 603 represents a switch for turning on or off the switch 502. Reference numeral 604 represents a switch for turning on or off the switch 401.

- Reference numeral 605 represents a switch for changing the speed control and the position control to the integration mode or proportion mode. Anintegration operation table and a proportion operation table of the gain table 506 is 22 switched for use by means of the switch 605. In a case where a robot arm is operated by means of a D.D. motor, an Integration operation mode control is performed for the purpose of positioning the robot arm, while a proportion operation mode control (compliance control) is performed for the purpose of holding an aritcile.

Reference numeral 606 represents a monitor output terminal for obtaining an output from the position control portion 500 through an S/H circuit 402. The output thus obtained is supplied to a display device, for example, an oscilloscope, for the purpose of being monitored.

Reference numeral 607 represents a pulse taking terminal for obtaining an incremental pulse signal through an up-down pulse g(nerator 608.

Reference numeral 609 represents an original-point signal terminal for obtaining outputs from the photodiodes G, and G2.

The outputs obtained from the pulse taking terminal 607 and the originalpoint signal terminal 609 are supplied to a controller (omitted from illustation). The rotational position of the motor is counted by means of the output from the pulse taking terminal 607 In the controller, while an original position is detected by means of the output from the original point signal terminal 609.

Symbol BS represents a data bus for transferring signals between the rotation detecting portion 300, speed 23 control portion 400, position control portion 500 and the tuning portion 600.

If the inertia J of the motor is oblique, the switch 502 is connected to the contact K2, whereby a known test signal is supplied to the position control means 505, and a signal thereby output by the position control portion 500 is monitored by means of an output terminal of the motor. The inertia value which has been set Is then adjusted by means of the inertia setting switch for the purpose of cancelling the distortion of the monitored waveform.

Fn and J may be set by an exterior controller as an alternative to the switches.

In the embodiment described above, although the structure is described in which the control parameter is read out f rom the gain table 506 when both the characteristic frequency fn and the inertial J are set by means of the servo tuning switch, a structure may be employed in which the control parameter is read out when either one- of fn or J is set.

According to the system described above, the following effects can be obtained.

1) In the motor from portion 100, since torque Is generated from the magnetic fields of the exciting coil of the stator and the static magnet, the ratio between torque and motor weight (abbreviated as "torque/ weight") can be enlarged. Furthermore, the static magnet the size of which 24 needs to be enlarged to a certain size for the purpose of obtaining the needed surface flux density is disposed on the stator side, therefore, the weight of the rotor can be reduced. As a result of this, torque/weight can be 5 enlarged in addition.

2) In the driving circuit 200, since a current detecting circuit including a small signal Isolator is used as the current detecting means (detecting means for feedback signals) for the motor coil, the exciting current can be detected at high accuracy and in a highly insulated manner, whereby a motor can be rotated with small speed ripples.

3) In the rotation detecting portion 300, since the slits for detecting positions are arranged in two stages and the difference of the number of the slits in two stages are arranged to be the same as the number of teeth on the motor, the phase difference between the teeth of the stator and those of the rotor of the motor can be directly obtained by making use of the phase difference between waveformed signals of the light penetrating through the slits. As a result of this, the rotational position of the motor and the rotational speed of the same can be detected at high resolution.

Furthermore, the encoder includes the original point detecting slits in addition to the position detecting slits provided. The signals from the encoder I/F3002 are supplied to the speed control portion 400 and the position detecting portion 500. As a result of this, the rotation detecting portion 300 has all the speed detecting, position detecting, original point detecting, and magnetic pole detecting functions.

4) In the servo tuning portion 600, when fn and J are set by means of the servo tuning switch, the most suitable parameter value Is read out from the gain table. The rotation of the motor Is controlled by means of thus obtained parameter value. As a result of this, the user does not need to set each control parameter value such as adjusting the gain of the circuit, whereby the servo system can easily be adjusted. Furthermore, only by setting fn and J, the gain setting of the MDA404 which is to be tertiary-controlled can be easily performed likely in a quadratic manner.

5) In the servo tuning portion 600, If the loadinertia of the motor is oblique, a known test signal is supplied to the position control means 505 for the purpose_ of taking the relevant output from the position control portion through the monitor output terminal 606, whereby the output is monitored. As a result of this, the inertia value which has been set is adjusted by means of the switch 602 so as to prevent the deflection of the monitored waveform. As a result of this, even if the load-inertia of the motor is oblique, the servo system can be easily adjusted.

Fig. 12 illustrates the structure of an essential 26 portion of a system according to another embodiment of the present invention, wherein a stopper portion 700 is placed between the motor portion 100 and the driving circuit 200.

The stopper portion 700 serves to stop the motor 100 by stopping the generation of electrical energy. When the motor Is rotated at high speed, that is, when the rotational speed of the motor exceeds a predetermined reference value, a coil L of the motor is, as shown in Fig. 13, connected to a parallel circuit comprising a resistor R,, and a capacitor C. On the other hand, when the motor rotates at a low speed, that is, when the rotational speed of the motor is lower than a predetermined reference value, the coil of the motor is, as shown in Fig. 14, shorted. Symbol,Rjo represents a coil resistance of the coil L. The coil L corresponds to the coil L, and coil L2 sh,own in Fig. 2.

A series resonance is generated between the capacitor C and the coil L by way of connecting the circuit as shown in Fig. 13, whereby phase V is prevented from becoming large. As a result of this, consumption of kinetic energy of the motor is increased. Furthermore, in order to decrease value Q in the resonance, the resistor R11 is connected in parallel to the capacitor C. As a result of this, the kinetic energy is further consumed. 25 Referring to F.ig. 12, the specific structure of the stopper portion will now be described. Referring to Fig. 12, ref erence numeral 710 27 represents an electrical -energy generation stopper circuit, reference numeral 720 represents a circuit for controlling the stoppage of generation of electrical energy for controlling the electrical energy generation 5 stopper circuit 710.

In the electrical energy generation stopper circuit 710, a rotation/stop switch SW10 is connected to a contact a, when the motor is rotated, while it is connected to a contact a2 when the same is stopped.

A stoppage-method selection switch SW11 is connected to a contact bi for the purpose of performing stoppage by means of a parallel circuit (resonance circuit) comprising the resistor R,, and the capacitor C. On the other hand, when the stoppag,e -method selection switch SW11 is connected to a contact b2, the stoppage is performed by way of shorting the motor coil L.

In the electrical-energy stoppage control circuit 720, reference numeral 721 represents an AND gate one of whose input terminals is applied with a control signal BR, while another Input terminal is applied with a high level signal. Reference numeral 722 represents a relay which switches the switch SW10 in accordance with an output from the gate 721.

Reference numeral 723 represents voltage generating means for generating voltage in response to a speed signal V from the motor. Reference numeral 724 represents a comparator for comparing an output voltage from the 1 28 voltage generating means 723 with a reference voltage VR, and generating a binary signal corresponding to the compared result. Reference numeral 725 represents an AND gate for obtaining an AND of an output from the comparator 724 and a control signal BR. Reference numeral 726 represents a relay for switching the switch SW11 in accordance with an output from the gate 725.

Claims

The comparison means which is claimed corresponds to the comparator 724,

while the stoppage switch means claimed corresponds to the portion comprising the AND gates 721 and 725, relays 722 and 726 and'the switch SW11.

An operation of the stopper portion whose structure is described above will now be described.

When the motor with such a stopper portion is rotated, the stopper signal BR is set to a low level. As a result of this, an output from the gate 721 becomes a low level, whereby the relay 722 makes the switch SW10 connect to the contact a,. As a result of this, an exciting current is supplied from the driving circuit 200 to the motor 100.

When the motor is stopped, the stopper signal BR is set to a high level. As a result of this, an output from the gate 721 becomes a high level, whereby the relay 722 makes the switch SW10 connect to the contact a2.

In this case, when the rotational speed V of the motor exceeds a predetermined reference value, the relay 72b makes the switch SW11 connect to a contact bl in $1 29 response to an output from the comparator 724.

As a result of this, a resonance circuit (a parallel circuit formed by the resistor R,, and the capacitor C) is connected to the motor coil L. In this resonance circuit, the kinetic energy of the motor is consumed. Provided that the phase V is it Is expressed by the following equation:

T n = tan-1 wherein:

LJ = Nr.

Nr e wL - wCR1 1 1 + (WCR11)2 RJO + R11 2 1 + (WCR1 l) 1 0. 0 0 5 : circular frequency of induction voltage of coil: constant: rotational speed of the motor. Reference numerals shown in the above described equation each represents resistance, inductance, and static capacity. experiences an aging, as shown in Fig. 15(a).

The rotational speed e of the motor is supplied as a signal V to the electrical energy stoppage control circuit 720.

k When the rotational speed V of the motor is lower than a predetermined reference value, the relay 726 makes the switch SW11 connect to the contact b2 in accordance with the output from the comparator 724.

As a result of this, the motor coil is shorted, and the kinetic energy of the motor is, as in the similar manner as the circuit shown in Fig.13, consumed. Provided that the phase Y is Y 1 in this stage, is expressed as follows:

15(a).

The agings experienced by the rotational speed e of the motor, exciting current I of the coil, and power-factor cos are as shown in Fig. 15(b).

In the stopper portion as described above, when the rotational speed of the motor is low, the phase Y becomes as expressed by Equation 6, while when it is high, the phase V becomes as expressed by Equation 5.

Energy P consumed in these circuits Is:

P = V 4 1 - cos Y tan-1 (wL) Rio The phase Y' experiences an aging as shown In Fig.

therefore, P becomes the maximum value when cos V = 1.

As can be clearly seen from the curve of cos V shown in Fig. 15(b) and Equation 7, when the rotational 31 speed of the motor Is high, cos -' " approximates 1 faster than cos Y1. Therefore, a method of stopping electrical energy generation using series resonance between a capacitor and a motor can faster consume kinetic energy of 5 the motor.

When the rotational speed of the motor is low, a circuit shown in Fig. 14 exhibits better efficiency. Therefore, when the rotational speed is lower than a certain level, the stoppage characteristics equivalent to the mechanical brake can be obtained by a simple structure by way of switching a circuit shown in Fig. 13 to that shown in Fig.14.

In the stopper structure, since a motor is stopped by way of selecting in accordance with the rotational speed of the motor the way of shorting the motor coil and the way of connecting the RC resonance circuit with the motorcoil, a motor can be effectively stopped through a wide range of the rotational speeds.

Fig. 16 illustrates another example of the structure of the rotation detecting portion of the system according to the present invention. This rotation detecting portion uses an encoder having slits in a sine-wave shape.

In Fig. 16, reference numeral 330 represents a plurality of light penetrating slits in a sine-wave shape disposed in the circumferential direction of a code plate 301 at a predetermined pitch.

The photodiodes 3081 and 3088 are, as shown in Fig.

32 17, disposed at a pitch P, which is the same as that of the light penetrating slits 330. Although the light penetrating slits 330 are disposed In the circumferential direction, they are shown in Fig. 17 in a developed manner 5 for the sake of the convenience of explanation.

The shape of the light penetrating slits 330 will now be described.

Fig. 18 shows the shapes of the light penetrating slits 330 wherein symbol 0 represents a rotational center of the code plate 301, symbols X and Y each of which represent a rectangular coordinate axis with point 0 as origin. Symbols in the figure represent:

N: the number of slits per round R: radius of a circle in the slit configuration 2K: difference between radii of circles inside and outside of the rlit configuration A: points on the inside circumference of the slits B: intersections between extensions of radii AO and the sine waveformed portions 0: angle determined by radii AO and X coordinate t: X coordinate of point A (x, y): coordinate of point B (xl, yl): coordinate of point A Consider 0' < e < 7P/2r AB K (1 + sine Ne) tan-' -v = tan-' therefore# "G t x and y can be expressed as follows:

33 wherein, x = t + k {1 + sin(N tan- 1 1 R; y t2 }cos (tan-1 I- _2L_t21 1 D + M + sin (N tan-1 -0 Osin(tan -1 xl = t y 1 =/R2 - t2 The region surrounded by the loci of points A and B is the light penetrating slit.

This can meet the region of 77P/ 2 < e < 2 JP.

Fig. 19 shows another example of the rotation detecting portion of the system designed according to the present invention.

This rotation detecting portion includes an encoder in which position-detecting lght penetrating slits configuration are disposed in two-stage manner, the slits being formed in a sine wave shape.

The outer slit configuration comprises m, light penetrating slits 331, while the inner slit configuration comprises m2 light penetrating slits 332, mi - m2 being arranged to be the same as the number of the teeth of the motor portion 100.

The light penetrating slit configuration 331 and 332 disposed in this twostage manner are provided for the purpose of detecting the setting of the teeth of the rotor of the motor in relation to the teeth of the stator.

Shift registers SR1 and SR2 turn on or of f in 34 sequence the switches SWI to SW8 to obtain at a certain timing of the outputs from the photodiodes 3081 to 3088 and photodiodes 3091 to 3098.

An operation of the circuit the structure of which is constituted as described above with reference to Fig. 19 will now be described.

The scanning frequency of the switches SW1 to SW8 is set at Sfs (fs represents the frequency of the waveforms of the outputs f rom LPFs 313 and 314).

The light beam which has passed through the outer light penetrating slits 331 is detected by the photodiode array-308, while the light beam which has passed through the inner light penetrating slits 332 is detected by the photodiode array 309. By scanning the detection signals 15 from the photodiode arrays with frequency 8f., signals fl(t) and f2M which have passed the LPFs 313 and 314 become as follows:

f A, sin (wt + Mle) 8 f 2(t) A2 sin (wt + M2e)...9o, wherein# Ar, A2: constant e: rotational an91 e of code plate w = 2n,f p and the phase difference between two signals is:

0 = (M 1 - M2) e . 0 a 10.

The relationship between phase difference, and the rotational angle e of the code plate will now be described.

A case will now be described providing that the number of the outer slits MI is eight and the number of the inner slits M2 is six. Furthermore, the number M of 5 teeth of the motor is set at two because 8 - 6 = 2.

The relationship between the detection signals from the photodiode arrays 308 and 309 and the rotational angle of the motor can be expressed as shown in Figs. 20(a) and 20(B).

As can be clearly seen from the figures, the shift between the detection signals (electrical angle) increases as 01,)2(2... in proportion to the increase in the actual rotational angle e (mechanical angle) of the code plate 301.

The shift between twp detection signals when the code plate is rotated by e can be expressed as follows from Equation 10:

(8 - 6) e On the other hand, the rotor of the motor also 20 rotates by e as the code plate 301 rotates by e. Since the number of the teeth of the motor is two, the teeth of the rotor of the motor and those of the stator shift by angle 2e. That is, the phase dif f erence detected by the code plate corresponds to the shift of the electrical angle between the teeth of the rotor of the motor and those of the stator of the same. Depending upon this relationship, the positional relationship between the teeth of the rotor 36 of the motor and those of the stator of the same is detected, and the commutation of the motor is thereby controlled.

In the above-described encoder, since each slit is formed in a sine-waveform, light which reaches each photodiode forms the sine-waveform. Since each photodiode generates an output corresponding to the area irradiated with light,the detection signal from the encoder is formed, as shown in Fig. 21, in a sine-waveform which approximates to the form of the reference wave in accordance with the arrangement of the photodiodes 3081 to 3088 As a result of this, the detection signal of the displacement convertor exhibiting high accuracy without any high frequency.components can be obtained.

The above described encoder will be helpful in terms of making the motor rotate smoothly when it is applied to controlling the rotational speed of the motor.

Fig. 22 illustrates another example of the rotation detecting portion of the system according to the present invention.

This rotation detecting portion includes a magnetic resolver.

In Fig. 22, Fig. 22(a) is a front elevational view of the device, Fig. 22(b) is a cross-sectional view taken along the line Z-Z of Fig.22(a).

Referring to the figures, reference numeral 810 represents a stator in which non-magnetic materials 814, 37 815 are respectively Interposed between three magnetic materials, that is, between 811 and 812, and between 812 and 813. Each of the magnetic materials 811, 812 and 813 has three salient poles 8111 to 8113, 8121 to 8123 and 8131 to 8133. Teeth 816 are formed at each of the outer ends of these salient poles.

The teeth of the salient poles on one magnetic material are disposed in the same phase, while the teeth on the magnetic materials 811, 812 and 813 are shifted with respect to each other by ((l/3) + ma) Pa (Pa represents a teeth pitch, and m represents an integer).

Each group of coils 8171 to 8173, 8181 to 8183 and 8191 to 8193 is wound around an associated one of the magnetic materials.811, 812 and 813.

Reference numeral 820 represents a rotor which is made of a magnetic material, and which is disposed outside the stator 810. Teeth 821 which oppose the teeth 816, and which have substantially the same pitch as that of the teeth 821 are formed on the rotor 820.

Reference numeral 822 represents a three-phase oscillator for applying sine-wave voltages Vo sin tit, Vo sin(wt + 1200) and Vo sin(L.-;t - 1200) to the groups of coils 8171 to 8173, 8181 to 8183, and 8191 to 8193, respectively.

Reference numeral 823 represents an arithmetic means which calculates the rotational angle and the rotational speed of the rotor 810 by making use of the currents 38 passed through the coils 8171 to 81731 8181 to 8183 and 8191 to 8193. Each current which passes through each coil is detected by way of connecting an associated one of a group of resistors in series manner to each coil, and measuring the voltages at two ends of the relevant resistor.

In a case where a three-phase coil is used, the number of the salient poles is not limited to- 9, as an alternative to It, it may only be 3na (na represents the number of the salient poles per one stator).

- The circuit diagram of the device described above is shown in Fig. 23. Referring to Fig. 23, reference numeral 8221. 8222 and 8223 represent oscillators for applying sine wave voltages Vo sin Lk, Vo sin ( Wt + 1200) and Vo sin (W t 1200) to 8171 to 81739 8181 to 8183, and 8191 to 81931 respectively.

The signal source corresponds to oscillators 8221 to 8223 Then, an operation of the above-described device of Figs. 22 and 23 will now be described.

The inductances L17, L18 and Liq of the corresponding coils 8171 to 81731 8181 to 8183 and 819, to 8193 is determined by means of each magnetic resistance R17, R,8 and Rig of the coils. Therefore, they are exuressed as follows:

L17 = n2 / R17 39 = n2 / (Ro + r. sin e) L18 = n2 / RIS = n2 / (Ro + ro sin(e + 1200) L19 = n2 / Rig = J / (Ro + r. sin(G - 1200)) wherein:

Ro, Ro: magnetic resistance n: number of coils When each coil is excited by the three-phase oscillator 822, currents 117, 18 and 119 which pass through the corresponding coils 8171 to 8173, 8181 to 81b3 and 8191 to 8193 can be expressed as follows:

117 Vo sin wt. w L17' Vo sin wt. 1 (Ro + ro sinO) W n2 = (a + b sine)sin wt 18 = {a + b sin(e + 12000 sin(wt + 120) 119 = {a + b sin(e - 120)} sin(wt - 1200) lz j wherein:

a, b: constant then, the sum of the currents 117, 118 and 119 is calculated and expressed as follows:

1 117 + 118 + 119 a {sin wt + sin(wt + 120) + sin(wt - 1200 + b (sin 0 sin wt + sin(O + 120)sin(wt + 120) + sin(O - 120)sin(wt - 120)} - -b- - cos (e + wt) + cos (e - We 2 {Cos(e - wt) - cos(O + wt + 240) + Cos(wt - e) cos(e + wt 2400)} =-' b cos(e wt) 2 ... 13 Since Equation 13 is the same as the equation of the output signal of the resolver the phase of which is converted at rotational angle e, the A/D converter becomes needless. Furthermore, the above-described optical encoder and an interface of the signal become the same, therefore, a common control circuit is employed.

From Equation 13, rotational angle e is obtained. Furthermore, since e = Vo t (Vo represents the angular velocity of the rotation of the rotor), the rotational speed of the rotor Is calculated by making use of the frequency of 9. Fig. 24 shows an example of the structure of the counter circuit using the position and speed detecting devices. 20 Referring to the figure, reference numeral 830 represents a position and speed detecting device according to the present invention, reference numeral 831 represents a wave f orm-shaping means for shaping the waveform of an output from the position and speed detecting device 830.

Reference numeral 832 represents a counter for counting the period of the shaped signal. Reference numeral 833 represents a microprocessor for obtaining rotational angle 41 9 by making use of the counted number of the period counter 832 as data.

Provided that a frequency of the output signal from the position and speed detecting device 830 when the rotor is stopped is 3 KHz and frequency counted by the period counter 832 to 3 MHz, the microprocessor 833 calculates rotational angle 9 from the following equation.

e = Z(Data - 1000) Data: value counted by the period counter 832.

The coil wound around the salient pole is not limited to the three-phase coil. Therefore, it may be a ka-phase coil (ka represents an integer). In this case, the number of the salient poles is arranged to be kana.

Although, in the embodiment, the structure is employed in which the phases of th teeth of the adjacent salient poles of the stator are shifted by Pa/3 with respect to each other, the rotor may be formed in three layers or the phases of the teeth in the adjusting layers may be shifted by Pa/3.

In the embodiment, although the structure is arranged to drive the coil by means of the voltage, whereby the rotational angle is obtained from the current passing through the coil, the coil may be driven by means of a current so that the rotational angle may be detected from the voltage applied to the coil.

By making use of the above-described rotation detecting portion, errors due to the eccentricity of the 42 rotor can be eliminated because the rotational angle is calculated from the sum of the signals detected by the plurality of coils disposed in the circumferential direction of the rotor. Furthermore, since no electric circuit is provided on inside of the rotation detecting portion, a good heat resistance can be obtained. Furthermore, the structure of the portion is arranged to be the same as that of the motor, assembling and adjustment of the portion can be conducted easily.

Fig. 25 shows another example of the structure of the rotation detecting portion, also in which a magnetic resolver is employed.

In Fig. 25, Fig.25(a) is a front elevational view, Fig. 25(b) is a cross-sectional view taken along the line Z1 - Z1 of Fig.25(a).

Referring to Fig.25, reference numerals 901 and 902 represent two annular stator members made of a magnetic material. Each stator member 901 and 902 has salient poles 9031 to 9034 and 9041 to 9044 at a rotational angular interval of 900. Each front end of the salient pole is provided with teeth 905 at pitch of Pb.

The neighbouring teeth on one stator member are shifted with respect to each other by (l/2)Pb For example, the phase of the teeth of the salient pole 9031 and those of the salient pole 9032 are shifted by (l/2)Pb.

A stator 907 is formed by the stator members 901 and 902, and a non-magnetic material member 906 which is 1 1 43 interposed therebetween, the members being stacked. In this case, they are stacked in such a manner that the phase of the teeth of the neighbouring salient poles are shifted by (l/4)Pb For example, the phase of the teeth 5 of the salient pole 903, and those of the salient pole 904, are shifted each other by (l/4)pb.

Reference numeral 9081 represents a coil wound around the salient poles 903i-and 9033. Reference numeral 9082 represents a coil wound around the salient poles 9032 and 9034, The above described coils 908, and 9082 form a single-phase of a coil. In the similar manner, the stator member 902 is wound with coils 909, and 9092.

Reference numeral 910 represents a rotor disposed outside of the stators 901 and 902. The rotor 910 has teeth 911 which oppose teeth 905, and which have the same pitch as that of the teeth 905.

Reference numeral 912 represents a signal source for supplying alternating voltage signals or alternating current signals to the different-phase coils 908 and 909.

The alternating current signals supplied to the coils 90d and 909 are shifted in phase by 900 with respect to each other.

Reference numeral 913 represents an arithmetic portion for detecting and adding and subtracting the voltages or currents between two ends of the coils 908 and 909, whereby the rotational position of the rotor 910 is calculated from the phase of the added or subtracted 44 signal, while the rotational speed is calculated from the frequency.

As a detecting circuit for detecting the current or voltage of two ends of the coil, for example, structures shown in Pigs. 26 to 28 are employed. A circuit shown in Fig. 26 is characterized in that voltages at two ends of the coil are detected. A circuit shown in Fig. 27 is characterized in that currents at two ends of the coil are detected. A circuit shown in Fig. 28 is characterized in that a transformer is employed for the purpose of performing the detection.

An operation of the above-described rotation detecting portion will now be described.

A power source 912 applies alternating voltage V1 cos (Lit + AA) to coils 9081 and 9082, while it applies altenating voltage V1 cos ( tj t + AB + 900) to coils 909 1 and 9092 (V, represents amplitude voltage, A A, A' B represent errors in electrical angle).

When the rotor 910 rotates by angle G, each voltage VS1, VS2, vci and VC2 at two ends of each coil 9081, 9082, 9091and 9092 is expressed'as follows:

VS1 V1 (1 + mb sin(e + AH Cos ( L"'t + AA)... (14) V s in(e + A) cos( Lkt + AA) (15) S2 V1 (1 - mb VC1 V1 (1 + Mb cOs(G + B)) sin( L.Jt + f..B) (16) V C2 -z V1 (1 mb C0s(O + B))sin(i,. t +.hB) (17) wherein:

mb: constant f -9 J A' S B: errors of mechanical angles The arithmetic portion 913 detects the voltage at two ends, and calculates as Equation 14 - 15 + 16 - 17, whereby the calculated value Vb Is obtained as follows:

v b = mb {s i n (wt + 0 + 6 A + AA) + s i n Nt + e + 6 B + AB) + 2. sin B -6 B-AA+6 COS(Wt + e + AB-6B+AA-6A 2 A) 2 --) ..W 018 By adjusting the electrical angle in Equation 18 and by setting the following relationship A B - 6B - AA +6A = 0' the secand term in the right hand of Equation 18 becomes zero, whereby the accuracy of the phase can be improved.

The number of the salient poles provided for one stator and the number of the stator members are not limited to the description in the embodiment.

In a case where one stator member is provided with nb salient poles (nb represents the magnification of two), while the number of the stator members is Kb, each value can be expressed as follows:

the shift of phases of teeth on neighbouring salient poles in one stator: Pb / 2 the shift of phases of teeth on the neighbouring salient poles when stator members are stacked:

((1 / 2kb) + Mb) (whenKb = 2) p 46 {(1 / kb) + Mb) (when kb is the integer other than two) wherein, mb: integer kb: the number of phase of coil.

the difference of phase between phases of the alternating voltage or alternating current for driving the coil:

3600 2kb (when kb = 2) 3600 kb (when kb is the integer other than two) In the embodiment, although the structure is described in which the phases of the teeth on the neighbouring salient poles of the stator are shifted, the rotor may be formed in stacked manner consisting of kb layers, and the phases of the teeth of the neighbouring layers may be, in the similar manner for the neighbouring salient poles in the embodiment, shifted with respect to each other.

According to the above-described rotation detecting portion, since the difference in voltage or current at two ends of a coil wound around the salient poles whose teeth are shifted by Pb / 2 is detected, the high frequency of even degree can be cancelled, whereby the rotation of a motor can be detected at high accuracy.

Furthermore, since the carrier Is cancelled In a differential manner in the calculation for obtaining Equation 18, temperature characteristics can be improved.

11 1 1- 47 Furthermore, the number of cores and circuits can be reduced to two thirds with respect to the three-phase rotation detecting portion shown In Fig. 22.

Furthermore, by making the number of teeth of a motor and those of a resolver the same, the commutation control can be conducted by making use of the phase of the resolver signal.

As described above, the system according to the present invention has various advantages, therefore it is effective when applied to driving joints of a robot of a multi-joint type.

48 CLAIMS: 1. A direct drive motor system comrpising: a motor portion of an inductor type; a rotation detecting portion for detecting the rotation of a rotor of said motor portion; a position control portion for obtaining the difference between an instruction signal on the rotational position and a detection signal from said rotation detecting portion, and outputting a control signal depending upon the thus-obtained difference by making use of a tertiary servo system with a software; a speed control portion for obtaining the difference between an output signal from said position control portion and said detection signal from said rotation detecting portion, and for outputting a control signal depending upon thusobtained difference; a driving circuit for detecting an exciting current passing through a coil of said motor portion, obtaining the difference between a detection signal of said exciting current and an output signal from said speed control portion, and controling said exciting current depending upon thus-obtained difference; and a tuning portion for adjusting servo systems of said speed control portion and said position control portion.

2. A direct drive motor system according to Claim 1, wherein said motor portion Is constituted by a rotor disposed in the outer portion thereof, and a stator 49 disposed in the inner portion thereof.

3. A direct drive motor system according to Claim 1, wherein said motor portion Is a three-phase motor of an inductor type.

4. A direct drive motor system according to Claim 1, wherein said rotation detecting portion outputs a position detection signal and a speed detection signal during rotation, said position detection signal being input to said position control portion, while said speed detection signal being input to said speed detecting portion.

5. A direct drive motor system according to Claim 1, wherein said rotation detecting portion comprises an optical rotary encoder, a code plate fitted to said rotor of said motor portion, slits which detect an, original point, and which are disposed at a predetermined pitch in the circumferential direction of said code plate, and slits which detect rotational position,and which are disposed in two-stage manner at a predetermined pitch in the circumferential direction of said code plate, the difference between the number of the outer slits of the two-stage and that of the Inner slits of the two-stage being arranged to be the same as the number of teeth provided for said motor portion.

6. A direct drive motor system according to Claim 5, 25 wherein said slits which detect rotational position are formed in a sine waveform.

7. A direct drive motor system according to Claim 1, wherein said rotation detecting portion is constituted by: a stator which has Ka na salient poles (Ka represents the number of the layers of said stator, while na represents the number of said salient poles per layer) on each outer end of which is formed teeth at a predetermined pitch, the phase of said teeth being shifted by ((1 / ka) + Ma)Pa (ma representing an integer, and Pa representing the pitch of said teeth) in accordance with the arrangement order of said salient poles; a rotor whose teeth oppose said teeth of said stator, said teeth thereof being formed at substantially the same pitch as that of said teeth of said stator; a ka -phase coil which is wound around said salient poles, one phase of said ka-phase coil being formed by a coil wound around salient poles having teeth of the same phase; a signal source for supplying Kam-phase alternating voltages or Ka-phase alternating currents the phases of which are shifted by (360 / K.)0 the alternating voltages or currents being supplied to-coils In each phase; and an arithmetic portion for detecting and adding said current or voltage applied to said coils in each phase, and obtaining the rotational position from the phase of an added signal, while obtaining from the frequency the rotational speed of said rotor.

8. A direct drive motor system according to Claim 1, wherein said rotation detecting portion comprises:

51 stator members each of which has nb (nb being a magnification of two) salient poles having teeth at a predetermined pitch at the front end thereof, the phases of said teeth on the neighbouring salient poles being shifted by Pb (Pb representing the pitch of said teeth), or coils to be described hereinafter being wound around neighbouring salient poles in such a manner that synthesized phases of change in reluctance are shifted by Pb / 2 between the neighbouring salient poles; the stator being constituted by kb stator members which are stacked, and in which the phases of said teeth of the neighbouring salient poles are shifted with respect to each other by U1 2Kb), + mb} Pb (when Kb = 2) or {(1 Kb) + mb} Pb (when kb is an integer othe.r than two) wherein, mb represents aninteger; a rotor having teeth which oppose said teeth of said stator, said teeth thereof being disposed at the same pitch as that of said teeth of said stator; a Kb-phase coil consisting of two sets of coils the phases of which are shifted by Pb / 2, one set of said coils being formed by the coil around the same-phase teeth of one stator member; a signal source for supplying alternating voltages or alternating currents of which phases are shifted by:

3600 / 2 kb (whenKb = 2) 3600 / kb (whenKb is integer other than two) to each 52 phase coil; and an arithmetic portion for detecting and adding and subtracting the currents or voltages at two ends of eachphase coil, and calculating the rotational position of said rotor from the phase of said adding and subtracting signals, and calculating the rotational speed from the frequency.

9. A direct drive motor system according to Claim 1, wherein said position control portion has a gain table in which characteristic frequency of said motor portion, load inertia value of the motor, and the most suitable parameter value corresponding to the correspondence of the characteristic frequency with said load inertia are contained.

10. A direct drive motor system according to Claim 9, wherein said tuning portion comprises a characteristic frequency setting switch in which characteristic frequency and load inertia are set in a plurality of steps within a predetermined range, and which reads out the most suitable control parameter value from said gain table depending upon at least either one of said characteristic frequency or said load inertia which has been set for the purpose of controlling the rotation of said motor portion, and a load inertia setting switch.

11. A direct drive motor system according to Claim 1, wherein said position control portion comprises a gain table in which the load inertia value applied to said 4 n--- 53 motor portion and the most suitable control parameter value corresponding to said load Inertia value are disposed in a corresponding manner, the motor comprising test signal generating means for generating a known test signal as a position instruction signal.

12. A direct drive motor system according to Claim 11, wherein said tuning portion comprises an inertia setting switch for setting inertia value within a predetermined range in a predetermined plurality of steps, and for reading out the most suitable control parameter value from said gain table at a set value for the purpose of controlling the rotation of said motor portion, and a monitor output terminal from which a control signal output from said position control portion is obtained when said test signal is applied. 1 13. A direct drive motor system according to Claim 12, wherein said speed control portion comprises a MDA to which a difference signal between a control signal from said position control portion and a detection signal from said rotation detecting portion is Input, and In which the gain thereof is set by means of said signal from said tuning portion.

14. A direct drive motor system according to Claim 1, wherein said driving circuit having a circuit for detecting an exciting current of said motor coil comprises:

a transformer having a primary and secondary coils, 4 54 a third coil disposed between said primary coil and said secondary coil, a pulse generator connected to said third coil, a first and a second non- linear circuits i.n which non-linear elements are connected In parallel In an inversed-pole manner, said non-linear elements having nonlinear voltagecurrent characteristics which allow currents to flow when a voltage exceeding a predetermined value passes through terminals, averaging means, and resistor; wherein an input circuit thereof is fornled by a circuit loop consisting of said primary coil, said first non-linear circuit and said resistor; while, an output circuit thereof is formed by a circuit loop consisting of said secondary coil, said second non-linear circuit and said averaging means; and by way of connecting in a series manner said resistor provided in said primary coil to said coil of said motor, a voltage which equivalents to the voltage at two ends of said resistor is arranged to be generated at two ends of said averaging means of said secondary circuit. 15. A direct drive motor system comprising: a motor portion of an inductor type; a rotation detecting portion for detecting the rotation of a rotor of said motor portion; a position control portion for obtaining the difference between an instruction signal on the rotational 4 position and a detection signal from said rotation detecting portion, and for outputting a control signal by makng use of a tertiary servo system with a software depending upon said difference which has been obtained; a speed control portion for obtaining the difference between an output signal from said position control portion and a detection signal from said rotation detecting portion, and for outputting a control signal by making use of said difference which has been obtained; a driving circuit for detecting an exciting current which passes through a coil of said motor portion, and for obtaining the difference between a detection signal of said exciting current and an output signal from said speed control portion, and for controlling said exciting current by makng use of said difference; and a tuning portion for adjusting servo systems of said speed control portion and said position control portion; and a stopper portion constituted by comparison means for comparing the rotational speed of-said motor with a reference value for the purpose of outputting a signal corresponding to the result of said comparison, and connection switch means, In accordance with an output from said comparison means, for shorting said coil of said motor if the rotational speed of said motor is lower than said reference value, and for connecting said coil of said motor to a parallel circuit constituted by a resistor and 4 56 a capacitor when the rotational speed of said motor is lower than said reference value for the purpose of stopping said motor. 16. A direct drive motor system comprising: a motor portion of an inductor type in which a rotor Is disposed on the outs ide thereof, while a stator is disposed on the inside thereof; a rotation detecting portion for detecting the rotation of said rotor of said motor portion, and for outputting a position detection signaland a speed detection signal; a position control portion comprising a gain table in which characteristic frequency of said motor portion, load inertia value of the same, and the most suitable control parameter value corresponding to said characteristic frequency, and said inertia value are disposed in a corresponded manner, and test signal generating means for generating a known test signal as a position instruction signal, in which the difference between said instruction signal on the rotational position and said position detection signal is obtained, for the purpose of outputting a control signal by making use of tertiary servo system with a software depending upon said difference which has been obtained; a speed control portion to which the difference between an output signal from said position control portion and said position detection signal is Input, and 4 57 which outputs a control signal by making use of a MDA whose gain is set by means of a signal from a tuning portion to be described hereinafter; a driving circuit for detecting an exciting current which is passed through said coil of said motor portion by means of a current detecting circuit in which a small signal isolator is used for the purpose of obtaining the difference between said detection signal of said exciting current and an output signal from said speed control portion, whereby said exciting current is controlled depending upon said difference; and a tuning portion comprising a characteristic frequency setting switch in which characteristic frequency and load inertia are set in a plurality steps within a predetermined range for the purpose of reading out the most suitable control parameter from said gain table depending upon at least one of set characteristic frequency and load inertia so as to control the rotation of said motor portion, and a load inertia setting switch, and a monitor output terminal from which a control signal output from said position control portion Is obtained when said test signal is applied, whereby servo systems of said position control portion and said speed control portion are tuned.

17. A direct drive motor system substantially as hereinbefore described with reference to Fig. 2 of the accompanying drawings.

58 18. A direct drive motor system substantially as hereinbefore described with reference to Figs 12 to 15(a) of the accompanying drawings.

19. A direct drive motor system substantially as hereinbefore described with reference to Figs. 16 to 18 of the accompanying drawings.

20. A direct drive motor system substantially as hereinbefore described with reference to Figs. 19 to 21 of the accompanying drawings.

21. A direct drive motor system substantially as hereinbefore described with reference to Figs. 22(a) to 24 of the accompanying drawings.

22. A direct drive motor system substantially as hereinbefore described with reference to Figs. 25(a) to 28 of the accompanying drawings.

Published 1988 at The Patent Office, State House, 66171 High Holborn, London WC1R 4TP. Further copies may be obtained from The Patent 0Ince, Sales Brancl,4 St Mary Cray, Orpington, Kent BR5 3BD. Printed by Multiplex techniques ltd, St Mary Gray. Kent. Con. 1187.